LONDON — Investigators believe that the masked killer known as “Jihadi John,” who fronted Islamic State beheading videos, is a British man named Mohammed Emwazi, two U.S. government sources said today.

BEIRUT — A U.S.-led alliance launched air strikes against Islamic State today in an area of northeast Syria where the militants are now estimated to have abducted at least 220 Assyrian Christians this week, a group monitoring the war reported.

DEBALTSEVE, Ukraine/KIEV — Kiev accused Russia today of sending more tanks and troops into eastern Ukraine and said they were heading toward the rebel-held town of Novoazovsk on the southern coast, expanding their presence on what could be the next battlefront.

UNITED NATIONS — Libya and Egypt asked the United Nations Security Council on Wednesday to lift an arms embargo on Libya, impose a naval blockade on areas not under government control and help build the country’s army to tackle Islamic State and other militants.

MAROUA, Cameroon/MAIDUGURI, Nigeria — Nigerian forces have killed more than 300 Boko Haram fighters during an operation to recapture 11 towns and villages since the start of the week, the military said today, as its war increasingly sucked in neighbors Cameroon, Chad and Niger.

COPENHAGEN — Known for a soft approach to security that emphasizes helping radical Muslim youths with housing and jobs, Denmark may face pressure after the Copenhagen attacks to prioritize tougher laws and more resources for the police.

PORT-AU-PRINCE — At least 16 people were killed and 78 injured early today when a carnival float hit a power line in Haiti’s capital Port-au-Prince, setting off a stampede by bystanders, officials said.

BAGHDAD — Iraqi security forces today repelled an attack by Islamic State insurgents against an airbase in Anbar province where U.S. Marines are training Iraqi troops, Iraqi and U.S. military officials said.

SANAA — Saudi Arabia has evacuated diplomatic staff from Yemen following a Shi’ite Muslim Houthi militia’s seizure of power there, joining Western countries who have also closed embassies due to fears of worsening violence.

MADRID — Three people were injured in an explosion at a chemical plant in northern Spain today and authorities advised residents of several small towns near Barcelona to stay indoors as a large toxic cloud spreads over the area.

ADEN, Yemen — Al Qaeda-linked fighters seized a large army base in a dawn attack in southern Yemen today, militants and residents said, hours after the United Nations warned that the country was on the brink of civil war.

President Barack Obama today confirmed the death of Kayla Mueller, a U.S. aid worker who had been held hostage by Islamic State militants, saying the United States would “find and bring to justice the terrorists who are responsible.”

UKRAINE — Rockets killed civilians and soldiers deep in Ukrainian government-held territory today and rebels pushed on with an assault to cut-off an army-held rail junction, setbacks that showed Kiev’s position worsening on the eve of peace talks.

DEBALTSEVE, Ukraine — Convoys of buses carrying many local residents to safety left the besieged town of Debaltseve in eastern Ukraine today as government forces kept up artillery fire to defend their positions against pro-Russian separatists.